The advent of micro-satellite and nano-satellite technology has provided an opportunity to insert sophisticated sensors and processing technologies into orbits of interest at low costs. Building a cluster of small satellites is generally cheaper, more robust, and more versatile than building one, large, monolithic satellite. Additionally, precision formation flying is critical to enable remote sensing space stations to improve both resolution and surface area coverage by orders of magnitude. Another advantage to precision formation flying of multiple nano-satellites is that it allows launch vehicles with small size limitations to assemble large, steady mirror apertures or large sample collection areas. For example, ultrahigh precision satellite clusters can be used for advanced geophysical monitoring to measure and monitor small changes in the movement of earthquake plates and gravity wave detection, whereas current GPS and standard laser range finders cannot. In another example, ultrahigh precision satellite clusters can be used for structuring large space telescopes and spectrometers for observing and characterizing earth-bound activities as well as near-earth orbit asteroids and comets.
Technology that depends on formation flying of nano-satellites critically depends on creating and maintaining precise formations. The least stringent requirements may require two satellites meters apart to maintain distance accuracy of 1 centimeter and a relative bearing of 1 arcminute while the most stringent requirements may require multiple satellites stationed kilometers apart to maintain distance accuracy of 1 nanometer and a relative bearing of 1 micro-arcsecond.
For example, one of the most challenging applications for formation flying thus far is that of the proposed MicroArcsecond X-ray Imaging Mission (MAXIM) project. According to the full MAXIM concept, the relative distance between the hub satellite and collector satellites needs to be precisely maintained within a few nanometers tolerance with a distance of approximately 200 meters between the satellites. The provision requirement for maintaining this distance, therefore, is 10 parts per trillion distance units. Most of the conventional propellant-based propulsion systems would not be able to handle this type of precision, such as gas hydrazine thrusters, pulsed plasma thrusters, hall thrusters, electrostatic ion engines, and field emission electron propulsion systems. Additionally, even if such thrusters were minimized to provide smaller, more accurate bursts of thrust, there remains a strong concern that the resulting propellant exhaust plumes may contaminate sensors and associated windows and optics.
To alleviate these concerns, several propellant-less formation flying methods have been proposed. Propulsive conducting tethers and spin-stabilized tether systems have been proposed in place of on-board propulsion systems to form and maintain satellite formations. Additional minimal thrust requirements can be handled through techniques such as the microwave scattering concept, the Coulomb force concept, and the magnetic dipole interaction concept. While such concepts offer intriguing possibilities for small arrays consisting of only a few spacecraft, implementing a system for dozens of satellites over large distances quickly becomes problematic.
For example, microwave scattering requires very high power consumption, requires large antenna arrays, and the scattered microwaves may electronically interfere with neighboring satellites. The Coulomb control system is limited to close formation (less than 50 m) plasma environments characterized by Debye lengths greater than the inter-vehicle separation, and requires very high voltage discharges which, in addition to consuming large amounts of energy, can damage instruments or throw off the accuracy of such instruments due to electrostatic discharge. The magnetic dipole interaction concept also requires close formations, and requires a very bulky and heavy system on the magnitude of several tons.
Therefore, there is a need in the art for a system and method to implement a system and a method for implementing satellite formation flying which is propellant-less, requires low power, is lightweight, uses little space, and provides for ultrahigh precision control of the distance and bearing between satellites.